1. Field of the Invention
The present invention relates to a glass, a component made of the glass and a plasma processing apparatus incorporating the component, and more particularly, to an Al-containing glass having a plasma resistance, a component for an electromagnetic wave-transparent window made of the glass, and a plasma processing apparatus incorporating the component.
2. Description of the Background Art
In the process of manufacturing LSI, LCD or the like, plasma that is generated by externally applying energy to reaction gas is widely used for etching, CVD and the like. In particular, the use of the plasma has been an essential technique in the process of etching. Now, increase in the size of the substrate to be processed with the plasma has been required that the plasma should uniformly be generated over a wider region.
FIGS. 1 and 2 show an example of the apparatus for such a plasma processing. The plasma processing apparatus shown in FIG. 1 has a rectangular parallelepiped-shaped reactor 31, which is entirely formed of aluminum. An upper opening of reactor 31 is sealed with a plate 34 such that reactor 31 is maintained gas-tight. Plate 34 is formed of a heat-resistant and microwave-transparent material with a small dielectric loss, e.g. quartz glass (SiO2). The upper part of reactor 31 is covered with a rectangular parallelepiped-shaped cover component 40. A dielectric line 41 is attached to the inside ceiling portion of cover component 40. Dielectric line 41 is made of a dielectric material such as a fluororesin e.g. Teflon(copyright), a polyethylene resin, a polystyrene resin or the like. Dielectric line 41 has a plate-shaped portion 41b and a tapered portion 41a that is an extension from the end of plate-shaped portion 41b and has an increased thickness. Tapered portion 41a is fit into a waveguide 51 connected to cover component 40. A microwave oscillator 50 is connected to waveguide 51. Microwave from microwave oscillator 50 is introduced into tapered portion 41a of dielectric line 41 via waveguide 51. The microwave is extended at tapered portion 41a and is propagated across the entire dielectric line 41. The microwave is reflected at the end surface of cover component 40, which is opposed to waveguide 51, and then the incident wave and the reflected wave are combined with each other, resulting in a standing wave in dielectric line 41. A gas introducing tube 35 is inserted into a wall of reactor 31 defining a processing chamber 32. A stage 33 is provided at the center of the bottom of processing chamber 32, on which a sample W is placed. Stage 33 is connected to a RF power-supply 37 of several hundreds kHz to ten and several MHz via a matching box 36. An exhaust vent 38 is provided at the side portion of the bottom of reactor 31.
In the plasma processing apparatus, the surface of sample W is processed by etching as described below. Processing chamber 32 is evacuated through exhaust vent 38 so that the pressure therein is reduced to a desired pressure, and reaction gas is then supplied from gas introducing tube 35 into processing chamber 32. Subsequently, microwave oscillator 50 oscillates microwave, which is introduced into dielectric line 41 via waveguide 51. At that time, the microwave evenly extends in dielectric line 41 by tapered portion 41a, resulting in a standing wave. The standing wave forms a leakage electric field at a lower part of dielectric line 41. The wave passes through plate 34 and enters processing chamber 32. In processing chamber 32 containing the reaction gas, plasma is generated by the microwave propagated into chamber 32. A radio frequency is applied from RF power-supply 37 through matching box 36 to stand 33, so that the surface of sample W is etched. Even if the apparatus has a large diameter of reactor 31 for the process of a large size of sample W, the microwave can be introduced uniformly into the entire region of reaction chamber 31, so that sample W can be subjected to relatively uniform plasma processing.
In addition to the essential performances of etching and film-forming, the plasma processing apparatus is also required to have some characteristics such as low contamination, reduced particles, long lives of consumable components, low operational cost and easy maintenance. In order to satisfy such characteristics, quartz glass, aluminum, alumina, stainless steel or the like is selected to conform the requirement for the materials of the components constituting the reactor and the internal structure thereof. The quartz glass is useful, among such materials, for the insulating component with low contamination and reduced particle release. For example, in the plasma processing apparatus described above, plate 34 that closes the opening of reactor 31 and separates the microwave-supplying portion from reactor 31 functions as a window for introducing microwave into processing chamber 32, and such a window has been conventionally made of quartz glass.
However, the quartz glass having good properties as mentioned above easily reacts with fluorine-containing plasma to form SiF4. SiF4 has a low boiling point and is easily vaporized, so that the quartz glass is rapidly etched in the fluorine-containing plasma and hence is worn away. Because the high purity quartz glass used in the process of LSI is expensive, such heavy abrasion would be a factor of a high manufacturing cost. Such heavy abrasion would also increase the frequency of changing the components and the time for such replacement may form a considerable part of the whole manufacturing time. As a result, the processing efficiency may be decreased and the manufacturing cost increased.
As a solution of the problem, Japanese Patent Application No. 4-356922 discloses a component for an electro-discharge and plasma process, which is made of high-purity polycrystalline alumina or high-purity monocrystalline alumina. This component has a microwave-transparent property and a resistance to the plasma derived from CF4+O2 gas.
However, when the alumina component as disclosed in the above publication is used as a microwave-introducing window in the electro-discharge and plasma process, the etching rate may be lowered, or the microwave-introducing window may be damaged due to the distortion of the alumina caused by heat. The inventors of the present invention have investigated the cause of the lowered plasma-processing rate among the problems associated with the use of the alumina microwave-introducing window. As a result, it has been found that the dielectric loss of the alumina is increased (whereas the Q value is decreased) as the temperature of the microwave-introducing window is increased during the plasma processing, so that the transparency to the microwave is reduced, causing the lowered plasma processing rate. It has also been found that a great thermal stress is generated in the alumina plate at a high temperature or with a wide distribution of temperature, resulting in cracks, because of the thermal expansion coefficient of the alumina plate larger than that of quartz glass. Additionally, ceramics such as alumina may contain a sintering agent to aid the formation of the sintered body. Such a sintering agent may constitute a factor in contamination.
Thus, the present invention is directed to solve the problems described above, and an object of the present invention is to provide a new material having a good plasma resistance.
Particularly, the present invention is directed to solve the problems associated with quartz glass, and another object of the present invention is to provide a component which has not only good properties similar to those of the quartz glass but also a corrosion resistance to plasma especially containing fluorine.
Yet another object of the present invention is to provide an application of the material having such a plasma resistance, and to provide a plasma processing apparatus incorporating a component made of such a material.
Still another object of the present invention is to provide a component of a plasma processing apparatus, having: electromagnetic-wave transparency suitable for generating plasma of high density; plasma etching resistance that is lacking in quartz glass; and a long life and crack resistance which are lacking in alumina, and to provide a plasma processing apparatus incorporating the component made of such a material.
According to the present invention, a new glass material is provided, which comprises a first glass phase consisting essentially of Si and O, and a second glass phase consisting essentially of Si, Al and O, wherein the second glass phase has a mass ratio of Al to Si of at least 0.01.
According to the present invention, is provided a plasma-resistant component made of the glass. Moreover, the present invention is also directed to a component for an electromagnetic wave-transparent window, which is made of the glass and is for use in constituting a window transparent to the electromagnetic wave.
Furthermore, the present invention is directed to a plasma processing apparatus that is for use in a process with plasma generated by using an electromagnetic wave. In the apparatus, a component made of the glass defined above is used as a component that is transparent to the electromagnetic wave so as to introduce the electromagnetic wave into a chamber where plasma is generated.
According to the present invention, a plasma processing apparatus includes: a reaction vessel which can be evacuated; a means for supplying a high-frequency electric power or electromagnetic wave into the reaction vessel; a means for supplying gas into the reaction vessel; and a sample stage on which a material to be processed is placed within the reaction vessel, wherein at least a part of the member to be in contact with plasma generated in the reaction vessel by the high-frequency electric power or electromagnetic wave is made of the glass defined above.
According to the present invention, another plasma processing apparatus includes: a reaction vessel which has an opening sealed with a sealing component and can be evacuated; a means for supplying a high frequency electric power or electromagnetic wave into the reaction vessel via the sealing component; a means for supplying gas into the reaction vessel; and a sample stage on which a material to be processed is placed within the reaction chamber, wherein the sealing component is made of the glass defined above.
The apparatus according to the present invention is especially useful as a plasma processing apparatus in which plasma is generated from gas containing fluorine. Moreover, the component according to the present invention is especially useful for the applications that are exposed to the plasma generated from the fluorine-containing gas.